but how do we really know?! Is there some scientific reasoning that backs up this claim?

I'm just looking out my window and millions of flakes have fallen into the great mass on the ground. once they touch the floor, they are lost, never destined to be treated as an individual again.

How is the theory proven with all the gazillion snow flakes that fall all over the world? Scientists are all everywhere all at once, y'know.

Have I given this too much thought? Answers on a reply to the usual address.